The invention relates to a method of securing a hazardous zone of a moved tool which has a point open to attack, in particular of a vertically downwardly moving upper tool of a bending press, with the hazardous zone being predetermined by the extent of the point open to attack of the tool and by the slowing down path of the tool along the direction of movement, with an optoelectronic sensor being moved with the tool and monitoring the hazardous zone and wherein, when an intervention into the hazardous zone is detected, a switching off is triggered for the immediate stopping of the tool movement. The invention further relates to a corresponding optoelectronic sensor.
The background of the invention is the endeavor to prevent injuries to an operator working at the moved tool of a machine, for example in that the operator supplies workpieces to be processed to the tool. In the case of the bending press, the upper tool can—without suitable securing measures—cause an injury to or a cutting off of the fingers or hands of the operator.
A direct risk of injury exists for the operator inside the hazardous zone which extends, starting from the point of attack of the tool, in the direction of movement of the tool. The point of attack of the tool includes, for example, a ram or a plunger, and it typically extends, for example, in particular with the bending press, along a bending line or cutting edge of the moved tool. The hazardous zone thus corresponds to a spatial region which is predetermined by the extent of the point of attack, on the one hand, and by the slowing down path of the tool, that is, by the path still covered by the tool after triggering of a switching off signal, on the other hand.
To secure this hazardous zone, it is known to move at least one transmitter device and one reception device of an optoelectronic sensor along with the tool. This sensor monitors whether an intervention into the hazardous zone has taken place by constantly transmitting and receiving a collimated transmitted light beam. If an intervention is detected by means of an interruption of the transmitted light beam, a switching off procedure is triggered which results in the stopping of the tool movement.
These known securing methods and securing sensors cannot provide the desired safety in all applications. This is initially due to the fact that the part of the hazardous zone actually monitored by the known sensors adopts a certain distance from the point of attack of the tool due to the slowing down path such that the part of the hazardous zone directly adjacent to the point of attack is not monitored. However, the known monitoring principle is above all essentially limited to the recognition of static interventions, that is, of interventions which already exist at the time of the tool movement and are only detected subsequently, that is, when the body part in question of the operator indirectly moves into the monitored part of the hazardous zone due to the moving along of the sensor.